A flashing check engine light in your 2022 Buick Encore isn't a subtle warning—it's your engine demanding immediate attention. When accompanied by code P0171 indicating "System Too Lean Bank 1," you're dealing with a fuel delivery or air metering problem severe enough to cause damaging misfires.
Why the Light Flashes
Your Encore's PCM flashes the check engine light when it detects severe, active misfiring that can damage the catalytic converter. Unlike a steady light that indicates stored issues, a flashing light means damage is occurring right now. P0171 adds context: the engine is running lean—too much air or not enough fuel—causing those misfires.
Understanding P0171
Bank 1 on the Encore's 1.4L turbocharged 4-cylinder refers to the bank containing cylinder 1 (on inline engines, this is the only bank). The oxygen sensor consistently reports excess oxygen in the exhaust, indicating incomplete combustion due to lean mixture.
Common Causes
Vacuum Leaks
Any unmetered air entering after the mass airflow sensor creates a lean condition. Common leak points on the 1.4L turbo include:
- Intake manifold gaskets
- Boost hose connections
- PCV system components
- Brake booster vacuum line
Mass Airflow Sensor Problems
A contaminated or failing MAF sensor underreports incoming air. The PCM then provides insufficient fuel for actual air mass. Aftermarket air filters using excessive oil often contaminate MAF elements.
Fuel System Issues
Weak fuel pump, clogged injectors, or fuel pressure regulator problems reduce fuel delivery, creating lean conditions throughout the operating range.
Exhaust Leaks
Leaks between the engine and upstream oxygen sensor allow atmospheric oxygen into the exhaust stream, making the sensor report lean even if combustion was correct.
Turbo Boost Leaks
The turbocharged engine relies on sealed boost plumbing. Leaks in intercooler hoses or pipes cause the engine to run lean under boost conditions.
Immediate Actions
When the check engine light flashes:
- Reduce speed and drive gently
- Pull over as soon as safely possible
- Don't repeatedly restart—each cold start while misfiring causes more converter damage
- Have the vehicle towed if necessary
Diagnostic Steps
- Scan for all codes: Check for additional codes that may indicate the root cause.
- Check fuel trims: Long-term fuel trim (LTFT) well above 10% confirms lean condition.
- Smoke test: Introduce smoke into the intake and boost system to find leaks.
- MAF sensor test: Compare readings to specifications and inspect for contamination.
- Fuel pressure test: Verify pressure at idle and under load.
Repair Costs
- Vacuum leak repair: $100-$400
- MAF sensor replacement: $150-$300
- Boost hose replacement: $100-$300
- Fuel injector service: $150-$400
- Catalytic converter (if damaged): $1,000-$2,500